In developing the correspondence between the Aikido techniques and those of Daito-ryu, I first identified the characteristics of the Aikido technique.

Before indulging some hopefully constructive critique, let me thank you for this analysis. It is very worthwhile.

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John Driscoll wrote:

For example, Shiho Nage of Aikido begins with Tori securing a grip on Uke's wrist and creating kuzushi, by manipulating Uke's arm, creating a sequential locking of Uke's elbow, shoulder, and spine.

More critically definitive of aikido, and aiki arts in general IMO, is the mechanism of obtaining kuzushi. Several schools of jujutsu do this essentially from an arm lock applying leverage through the elbow joint to create kuzushi. This is simply a linear reaction to strain, and not aiki. Cranking, or the torsional equivalent of leverage, is the same thing.

Conversely, the sharp spiral tightening in aikido and other more expressly aiki arts should provoke an involuntary reflex in the body, in this case the triggering of extensors, and hence the tippy-toe reaction of uke for the entry. The inverse form of this action will generate the reverse and trigger flexors to drop him.

The manner of the application of the torque (or in some cases a more linear wave) is different from what you seem to imply. It is just as critical and must be of the rhythm of furitama in order to effect proper aiki. It may be only a single sharp pulse in that overt action -- or an almost imperceptible amplitude but continuous furitama that enables an kind of tactile echo-sounding 'sensitivity' of internal structure (kokyu tanden ho) that leads one where to move for kuzushi without any applied overt torquing or levering of the limb or body.

That manner of action defines it as an aiki waza and distinguishes it from the simple applied torsion or straight arm locks (some of which you describe) which are applying an overt leverage (albeit one the joint cannot oppose) and those that apply the "sequential torque" as you call it. The action is not an actual "cranking" torque or a leverage, though it is inherently related. In a beam, applied bending forces are resisted by resulting internal shears. The relationship is that if you create bending (torque or leverage) you get spontaneous shear -- if you create shear you get spontaneous bending. Aiki is in the latter category, which can be shown by a literal kitchen-table model.

Take a dishrag from your kitchen. Hold it between your hands. Try to use the dishrag to push one hand with the other. It won't work because it is as limp as ... um... a dishrag.

Now twist the dishrag between your hands. Keep twisting until all the slack is wrung out. You can now push one hand with the other, like it was a slightly bendy stick. Now, push the hands together, feel it compress slightly without bending the rag much. Now -- without releasing the slight compression -- release the twist slightly in one hand -- the rag will now bend spontaneously in response to the buckling shear created by the effective lengthening of the rag in untwisting it -- and at a joint that you did not even see when it was all twisted up.

Conversely, if you allow an end to remain free to move as you twist, it coils up in tension from the continued torsional shortening while essentially still slack (vice a torsional strain from resistance to the movement, once some tautness is obtained).

These are the purely mechanical part of the respective inverse actions of aiki -- which involves creating spontaneous action in a structure very different from the direct action of a pure torque or leverage on a resisting structure. The neuromuscular part in manipulating reflexes is noted above.

These two mechnical actions are the closing and opening forms of asagao in the DTR terminology. The attention of some to the issue of "slack" in the structure is generally correct -- but -- this seems IMO misinterpreted in the way they typically describe it .

Slack can be poor structure -- or it can be a structural reserve. It does not necessarily indicate poor structure --as with the dishrag -- slack and taut can be converted at need to different effect. But the inability to shift between them fluidly, and the lack of sensitivity to that critical cusp state -- not quite slack, not quite taut -- WOULD indicate poor structural sensitivity. Simply making the structure taut does not insulate it from the application of aiki -- as shown by our dishrag, and there are other neuro-muscular things going on that critical slack can either provoke or defeat in application. It also seems to be what O Sensei addressed in his discussion regarding aiki training as the "softening of joints."

If the shape of the action is correct in that way -- as well as the rhythm, uke folds up like a cheap cardboard playhouse -- and the "technique" is simply defined by the way in which the suddenly mobilized joints display themselves. Essentially, the action of aiki shapes the failure mode of a structure and then shifts it out of its stability profile -- but not locking it up -- it departs stability with one, and only one, degree of freedom -- the form of the technique being applied, which it follows like a leaf down a sluice.

If the action results in an overt resisted torque or countered lever, then the manner of action has not been achieved in aiki or aiki is lost in the course of application. A throw progressively tightens (closing asagao) or loosens (opening asagao) and then reverses the action at a cusp -- like a ski jump, or in osae waza continues the same action without reversal but the degree of freedom is then closed off by an obstacle (typically, a wall, floor, knee, hip, or whatever).

Quote:

John Driscoll wrote:

Further, it appears Morihei Ueshiba incorporated in Aikido the version of the Daito-ryu technique, which he believed to be the one generating the most power and versatility of application, with modification, as he deemed appropriate.

His rubric ( and method) for arriving at what was "appropriate" is what I think is important. I submit that the Aikido corpus pruned from the DTR syllabus represent those applications lending themselves most readily to the described manner of action. I submit that they became the "aikido corpus" because when O Sensei intuitively grasped the essential nature of manipulating structure and reaction in this way -- they were the types of techniques he most readily "found" when acting spontaneously, in takemusu aiki. He therefore tended to repeat those essential forms in as many variations as they spontaneously appeared to him, rather than demonstrating them as a prefigured or intended corpus of techniques. Those that did not lend themselves to this manner of action at all, or as easily, just fell away from disuse.